- 學位論文
薄膜污塞線上光學偵測技術之評估
Evaluation of On-line Membrane Fouling Monitoring Technique Using a Photointerrupt Sensor
摘要
在薄膜生物反應器中，膜污塞的程度會因為進水水質不同、操作方式不同和預處理效果不同而有所差異，在過去的研究中許多學者都僅針對於減少污塞發生的方法進行研究，對於膜表面濾餅層分佈型態研究的學者並不多。實際上，進行分離操作時膜表面濾餅層的生成並非呈現均勻分佈，藉由觀察濾餅層厚度分佈情形可進而探討濾餅層於膜表面局部區域快速形成之原因，據此對膜組件進行最適化，可有效增加膜的使用壽命並降低設備運轉成本，因此如何精確的觀察膜表面濾餅層分佈亦是當前重要的課題。 在本研究中利用光遮斷感應器的電壓變化觀察濾餅的生成情形，研究過程中發現當同時使用多顆探針時，若探針間距過於接近，會導致反射光相互干擾產生誤差，因此當使用多顆探針時應保持探針的間距為30 mm以上，才能避免相互干擾的誤差產生。 最後，在本實驗中利用多顆探針觀察曝氣對膜表面濾餅層生成的影響，實驗中將探針擷取之數據經過分析轉換為立體分佈圖後，清楚觀察到曝氣對於濾餅層的影響，本研究結果顯示此光學偵測技術確實可作為設備操作人員控制膜清洗時機與膜組件最適化之工具，並具有低成本與高準確性的優勢。
並列摘要
Membrane fouling and subsequent flux decline are undesirable but inevitable problems in membrane filtration processes for water treatment. To deal with these formidable obstacles, numerous methods have been adopted by experts in the discipline of water treatment membrane process; for example, development of low fouling membranes, design of high efficiency modules, selection of optimal operational strategies, and several improvements in peripheral control, monitoring and cleaning techniques. However, the gradual development and improvement of these methods limit the competitiveness of the process and its wide acceptance during past three decades. An early warning technique for fouling problem in water treatment membrane process is crucial to the improvement of membrane process operation as well as to the development of fouling prevention strategy. Usually, the problems of severe flux decline or process failure are noticed if the quality of product or produced water fails given standards. This is the most expensive method of fouling monitoring, but still widely adopted in practical. Until the end of the last millennium, researchers have begun to be aware of the importance of in situ understanding as well as online monitoring of the fouling growth. Several in situ monitoring techniques have been developed in the laboratory to reveal the growth mechanism of fouling layer in membrane filtration processes. Nevertheless, process oriented, reliable and predictable online monitoring techniques for onsite fouling analysis and control are still few. In this study, an integrated online monitoring technique that can provide dynamic and real-time information of a fouling process has been developed. An application to water treatment membrane process of this monitoring technique has been preliminarily demonstrated with a line-source photo sensor. Results of the online dynamic analysis depict that this technique provides process-oriented capability of in situ measurement of fouling layer thickness. The example reported is part of this concept; the integrated online dynamic monitoring technique is being applied to a lab-scale water treatment unit with a line-source photo sensor to provide real time 3-D profile of fouling layer thickness. With sensors which allow for scanning of each membrane surfaces on demand, the integrated online dynamic monitoring technique would be feasible to be directly applied in commercial membrane module for water treatment. Moreover, it is a surprising fact that so many robust devices are available for fouling monitoring but they have never moved beyond laboratory status. Significant challenges remain to improve these available monitoring techniques to bridge the gap between laboratory setting and field application.